The invention relates to a method of communication between a vehicle and a wayside control unit for controlling and inductive energy or power transfer to the vehicle, and an arrangement of the vehicle and an inductive power transfer station.
Electric vehicles, in particular a track-bound vehicle, and/or a road automobile, can be operated by electric energy which is transferred by means of an inductive power transfer. Such a vehicle may comprise a circuit arrangement which can be a traction system or a part of a traction system of the vehicle. Also, a vehicle can comprise a so-called receiving device adapted to receive an alternating electromagnetic field and to produce an alternating electric current by electromagnetic induction. Such a receiving device can comprise or provide the circuit arrangement, in particular a so-called secondary winding structure. Furthermore, such a vehicle can comprise a rectifier adapted to convert an alternating current (AC) to a direct current (DC). The DC can be used to charge a traction battery or to operate an electric machine. The rectifier converts the AC provided by the receiving device into the DC.
The inductive power transfer is usually performed using a primary unit which generates the alternating electromagnetic field by a primary winding structure and a secondary unit which comprises the receiving device for receiving said electromagnetic field. The primary unit and the secondary unit can e.g. each comprise a set of three-phase windings. A set of windings of the primary unit can be installed on the ground (primary windings) and can be fed by a wayside power converter (WPC). A set of windings of the secondary unit is installed on the vehicle. For example, the second set of windings can be attached underneath the vehicle, in the case of trams under some of its wagons. The set of windings of the primary unit can also be referred to as primary side, wherein the set of windings of the secondary unit can be referred to as secondary side. The first and the secondary side can be part of a high frequency transformer to transfer electric energy to the vehicle. This transfer can be done in a static state (when there is no movement of the vehicle) and in a dynamic state (when the vehicle moves).
U.S. Pat. No. 7,454,170 B2 discloses an inductive transmission system for inductive transmission of power and full duplex data signals between first and second devices. The transmission system includes a bi-directional inductive channel between the two devices, a transmitter for transmitting a power signal at a first frequency from the first device to the second device over the inductive channel, a first modulating device for modulating a first data signal at a first modulation frequency, and a second modulating device for modulating a second data signal at a second modulation frequency. Further, the transmitters transmit the modulated first data signals from the first device to the second device over the inductive channel, and transmit the modulated second data signals from the second device to the first device over the inductive channel. The first modulation frequency and the second modulation frequency are at least a factor two apart.
An inductive power transfer station can comprise one or multiple primary unit(s), wherein each primary unit can comprise a primary winding structure for generating the power transfer field. This allows inductive power transfer to multiple vehicles.
To manage the inductive power transfer to the vehicle, charging-related data needs to be transmitted between the vehicle and the inductive power transfer station, in particular a control unit of the inductive power transfer station for controlling the inductive power transferred to the multiple vehicles. Such data can encode information concerning e.g. a charging state of a vehicle-sided battery, e.g. a traction battery, a maximum admissible power to be transferred but also information regarding the billing of the transferred energy.
In particular, in the case of multiple primary units controlled by one common control unit, there is the problem of assigning a vehicle to a primary unit by which the inductive power transfer to the vehicle will be conducted. Only a correct assignment will guarantee that correct charging parameters will be used by the control unit in order to generate the power transfer field.
Another problem is that charging-related data, in particular data related to billing information, is confidential data. Thus, a secure communication between the vehicle and the control unit is desirable.
Yet another problem is that inductive power transfer usually requires a correct positioning of a secondary winding structure relative to a primary winding structure in order to maximize the amount of transfer power but also in order to meet safety requirements and provide an electromagnetic compatibility.
It is an object of the present invention to provide a method of communication between a vehicle and a wayside control unit of a system for inductive power transfer, a vehicle and an arrangement of the vehicle and the wayside control unit which allow a safe communication of charging-related data in between the vehicle and the control unit.
It is a main idea of the invention to provide a first and at least a second communication link which are independent of each other, wherein data transmitted via the second communication link is used to authenticate charging-related data transmitted via the first communication link.
Another main idea of the invention is to use the second communication link for a correct positioning of the vehicle-sided secondary winding structure relative to a primary winding structure.